1. Technical Field
The present invention relates to a polymer optical waveguide and a method for producing the same.
2. Related Art
In the technical field of high-speed signal transmission, electricity, which is widely used as a transmission medium, is approaching limits to its speed of transmission. Thus, optical transmission is expected to eventually replace electrical transmission, and attention is therefore being paid to optical interconnection, which utilizes optical links between instruments and appliances, and/or between boards and/or between chips inside instruments and appliances.
As a technology that enables optical interconnection, a polymer optical waveguide including a core through which light propagates, and which is formed from a polymer having a high refractive index, and a cladding which surrounds the core and is formed from a polymer having a low refractive index, is attracting attention since the materials used therein are flexible, the production costs are low, and the like.
As techniques for producing such a polymer optical waveguide, methods such as the following have been proposed.    (1) A method including impregnating a film with a monomer, selectively exposing a core portion to light so as to change the refractive index at the core portion, and adhering additional films to the film (selective polymerization method).    (2) A method including forming a core layer and cladding layers by coating, and forming a cladding by reactive ion etching (reactive ion etching (RE) method).    (3) A method using photolithography in which a UV-curable resin obtained by adding a photosensitive material to a polymer material is exposed to UV light and developed (direct exposure method).    (4) A method using injection molding.    (5) A method including forming a core layer and cladding layers by coating and exposing a core to change the refractive index of the core (photobleaching method).    (6) A method of producing a polymer waveguide using a mold.
The polymer waveguides produced by the various methods described above are capable of guiding optical signals only, and for example, in the case of carrying out transmission of low-speed electrical signals or supply of electrical power in addition to transmission of high-speed optical signals between printed boards or between modules, it has been necessary to separately install conductive wires in addition to optical wiring.